Integrated circuit calibration architecture

ABSTRACT

A calibration architecture that enables accurate calibration of radio frequency (RF) integrated circuits (ICs) chips used in transceiver RF systems in a relatively simple testing environment. Embodiments of the invention include one or more on-chip switchable internal calibration paths that enable direct coupling of a portion of the on-chip circuit to an RF test system while isolating other circuitry on the chip. Periodic self-calibration of an RF IC can be performed after initial factory calibration, so that adjustments in desired performance parameters can be made while such an IC is embedded within a final system, and/or to take into account component degradation due to age or other factors.

CROSS-REFERENCE TO RELATED APPLICATIONS Claim of Priority

This application is a continuation-in-part of and claims priority tocommonly owned and U.S. patent application Ser. No. 15/195,379, filedJun. 28, 2016, entitled “Integrated Circuit Calibration Architecture”,now U.S. Pat. No. 9,717,008, issued Jul. 25, 2017, the disclosure ofwhich is incorporated herein by reference in its entirety.

BACKGROUND (1) Technical Field

This invention relates to electronic circuits, and more particularly tocalibration and testing architectures for radio frequency integratedcircuits.

(2) Background

Radio frequency (RF) integrated circuits (ICs) may include a number ofdifferent RF signal paths and involve multiple inputs and outputs, suchas is the case with multi-antenna/multi-transceiver RF ICs. Such RF IC'smay be used, for example, in communication or radar systems that utilizebeamforming techniques for directional signal transmission and/orreception. Beamforming combines transmit/receive elements in a phasedarray in such a way that signals at particular angles experienceconstructive interference while other signals at other angles experiencedestructive interference. Beamforming can be used at both thetransmitting and receiving ends of a communication system in order toachieve spatial selectivity. Another advantage of beamforming is thatthe directional nature of the link means that less power needs to betransmitted to achieve a good signal to noise ratio at the receiverbecause all of the signal energy is directed at the receiver rather thanbeing dispersed omni-directionally.

The quality of beamforming depends on how accurately multipletransceivers on an IC track each other with respect to at least phaseand signal amplitude. It is possible to adjust the settings of differenttransceiver phase shifters circuits and attenuators circuits (positiveand negative) if the performance of each transceiver is known inadvance. Measured differences between transmitted and received signalsmay be used to adjust (calibrate) the phase and/or signal amplitudestate of one transceiver with respect to the other transceiver. However,accurate calibration measurements of such performance are difficult toobtain in an assembled final system where all measurements need to bedone “over the air”, meaning actually transmitting a signal (which maybe varied over a band of frequencies) from one transceiver through anantenna and receiving that signal in a different transceiver through anantenna. Such measurements require relatively elaborate testingequipment capable of dealing with high frequency RF signals (e.g., up to30 GHz or more) and may be heavily influenced by environmental factorsin the test set-up that alter, shield, attenuate, distort, or otherwiseaffect the transmitted and received signals. Furthermore, the accuracyor performance of a transceiver will vary over the possible bandwidth ofthe system, and therefore adjustments may need to be made dynamicallydepending on the instantaneous frequency of operation.

Accordingly, there is a need to be able to calibrate RF ICs used intransceiver RF systems more accurately, preferably with a simplertesting environment. The present invention meets this need and more.

SUMMARY OF THE INVENTION

The invention encompasses a calibration architecture that enablesaccurate calibration of radio frequency (RF) integrated circuits (ICs)chips used in transceiver RF systems in a relatively simple testingenvironment. Embodiments of the invention include one or more on-chipswitchable internal calibration paths that enable direct coupling of aportion of the on-chip circuit to an RF test system while isolatingother circuitry on the chip.

Advantages of various embodiments of the invention include a calibrationarchitecture that enables accurate calibration of RF ICs used intransceiver RF systems in a relatively simple testing environment thatis done by direct connection (as opposed to “over the air”) atsignificantly lower frequencies. Accordingly, environmental factors inthe test set-up that alter, shield, attenuate, distort, or otherwiseaffect transmitted and received “over the air” test signals areeliminated or significantly mitigated. Further, periodicself-calibration of an RF IC in accordance with the present inventioncan be performed after initial factory calibration, so that adjustmentsin desired performance parameters can be made while such an IC isembedded within a final system, and thus take into account the actualusage environment (including, for example, temperature, electrically“noisy” circuitry, parasitic electromagnetic coupling, etc.). Periodicself-calibration also allows re-characterization of such an RF IC totake into account component degradation due to age or other factors.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram of a first embodiment of an RF IC (or “chip”)with integrated calibration circuitry suitable for use in a transceiverRF system.

FIG. 1B is a block diagram of the input/output circuit of FIG. 1A.

FIG. 1C is a block diagram of the multi-way switch complex of FIG. 1A.

FIG. 2 is a block diagram showing a switch configuration for testingphase-attenuation Cores 1 and 2 of the RF IC of FIG. 1A.

FIG. 3 is a block diagram of a second embodiment of an RF IC withintegrated calibration circuitry suitable for use in a transceiver RFsystem.

FIG. 4A is a block diagram of a portion of the circuitry of FIG. 1A orFIG. 3 showing an indirect intermediate frequency path bypass switch

FIG. 4B is a block diagram of a portion of the circuitry of FIG. 1A orFIG. 3 showing a direct IF bypass switch.

FIG. 5 is a block diagram of a third embodiment of an RF IC withintegrated calibration circuitry suitable for use in a transceiver RFsystem.

FIG. 6 is a flowchart showing a first method for calibrating a radiofrequency (RF) integrated circuit.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION OF THE INVENTION

The invention encompasses a calibration architecture that enablesaccurate calibration of radio frequency (RF) integrated circuits (ICs)chips used in transceiver RF systems in a relatively simple testingenvironment. Embodiments of the invention include one or more on-chipswitchable internal calibration paths that enable direct coupling of aportion of the on-chip circuit to an RF test system while isolatingother circuitry on the chip.

Basic Core Circuit Testing Configuration

FIG. 1A is a block diagram 100 of a first embodiment of an RF IC 102 (or“chip”) with integrated calibration circuitry suitable for use in atransceiver RF system. This particular example of an RF IC 102 isconfigured to be coupled to transmit circuitry 104 (labeled “Tx Ckt”)through an isolation and/or drive buffer 106 to a conventional imagereject mixer 108, which in turn is coupled to a multi-way switch complex110 (see also FIG. 1C). Also coupled to the multi-way switch complex 110through a conventional image reject mixer 112 and an isolation and/ordrive buffer 114 is receive circuitry 116 (labeled “Rx Ckt”). Thetransmit circuitry 104 and the receive circuitry 116 generally willoperate at baseband frequencies, but some embodiments may operate atintermediate (IF) or RF frequencies (with appropriate adjustments inother circuitry, such as the image reject mixers 108, 112, if needed;more specifically, if the transmit circuitry 104 and the receivecircuitry 116 operate at RF frequencies, then the image reject mixers108, 112 may be omitted).

The transmit circuitry 104 and/or the receive circuitry 116 may beon-chip, or optionally may be on off-chip, as suggested by the dottedboxes around both circuit blocks. In some embodiments, one or bothbuffers 106, 114 and one or both image reject mixers 108, 112 may beexternal to the RF IC 102. Accordingly, in some configurations of the RFIC 102, the transmit circuitry 104, drive buffer 106, and image rejectmixer 108 can be considered to define a primary RF transmission path Tx,while in other configurations, the drive buffer 106 and image rejectmixer 108 can be considered to define the primary RF transmission pathTx, and in yet other configurations, the input to the multi-way switchcomplex 110 can be considered to define the primary RF transmission pathTx. Similarly, in some configurations of the RF IC 102, the image rejectmixer 112, buffer 114, and receive circuitry 116 can be considered todefine a primary RF reception path Rx, while in other configurations,the image reject mixer 112 and buffer 114 can be considered to definethe primary RF reception path Rx, and in yet other configurations, theoutput of the multi-way switch complex 110 can be considered to definethe primary RF reception path Rx.

In the illustrated example, the multi-way switch complex 110 allowsselective coupling of either the transmit circuitry 104 or the receivecircuitry 116 to one or more phase-attenuation cores 120 through acorresponding divider/switch 122 a, 122 b (see also FIG. 1C for moredetails of the multi-way switch complex 110). A divider/switch 122 a,122 b, may be, for example, a Wilkinson power divider (which optionallymay be bypassable through a parallel switch path), or a set of switchesfor directing transmitted or received signals between the multi-wayswitch complex 110 and one or more of the phase-attenuation cores 120.If needed for impedance matching, the multi-way switch complex 110 maybe coupled to the divider/switches 122 a, 122 b through a transmissionline (not shown).

The four illustrated phase-attenuation cores 120 may include a phaseshifter circuit and a signal amplitude control circuit, such as anattenuator circuit that provides a reduction in amplitude of an appliedsignal, or an amplifier that amplifies an applied signal and thuseffectively provides “negative attenuation” (e.g., a variable gainamplifier); one or both of the phase shifter circuit and/or signalamplitude control circuit may be adjustable or variable. More than orfewer than four phase-attenuation cores 120 may be included on the RF IC102; in general, the number of phase-attenuation cores 120 may rangefrom 1 to N, where N is limited only by practical IC fabricationconstraints. Each phase-attenuation core 120 is shown connected to anassociated input/output circuit 124 (to avoid clutter, only oneinput/output circuit 124—indicated by a dashed-line oval—is numbered).In some embodiments, the combination of a phase-attenuation core 120 andan associated input/output circuit 124 comprises a transceiver front-endcircuit, while in other embodiments, a phase-attenuation core 120 alonecomprises a transceiver front-end circuit (e.g., where thephase-attenuation cores 120 of an RF IC 102 are configured to be coupledto corresponding external input/output circuits 124).

FIG. 1B is a block diagram 150 of the input/output circuit 124 of FIG.1A. In the illustrated example, a pair of single-pole, single-throw(SPST) switches 152, 154 may respectively select a transmit path TX or areceive path RX. The SPST switches 152, 154 may be implemented, forexample, as one or more field effect transistors (FETs), or may bemicroelectromechanical system (MEMS) devices, and are preferablyincluded on-chip. Further, in some embodiments, a single-pole,double-throw (SPDT) switch may be used in place of the SPST switches152, 154, and in many cases would be preferred.

The transmit path TX includes one or more amplifiers 154 a, 154 b, whichmay be on-chip, off-chip, or a mix of on-chip and off-chip (FIG. 1Ashows such a mix). One or more of the transmit path TX amplifiers (e.g.,amplifier 154 a) may be an isolation and/or drive buffer amplifier(which may only have unity gain in some cases). At least one of theamplifiers 154 a, 154 b may be a power amplifier.

The receive path RX also includes one or more amplifiers 156 a, 156 b,which may be on-chip, off-chip, or a mix of on-chip and off-chip (again,FIG. 1A shows such a mix). One or more of the receive path RX amplifiers(e.g., amplifier 156 b) may be an isolation and/or drive bufferamplifier (again, which may only have unity gain in some cases). Atleast one of the amplifiers 156 a, 156 b may be a low noise amplifier(LNA).

A single-pole, double-throw (SPDT) switch 158 selectively couples eitherthe transmit path TX or the receive path RX to an antenna 160. The SPDTswitch 158 may be implemented, for example, as one or more FETs or MEMSdevices. In some embodiments, a pair of SPST switches (similar to SPSTswitches 152, 154) may be used in place of the SPDT switch 158.

In a typical configuration, as suggested by the dotted line 162,amplifier 154 a is an on-chip buffer amplifier, amplifier 154 b is anoff-chip power amplifier, SPDT switch 158 is off-chip, amplifier 156 ais an off-chip LNA, and amplifier 156 b is an on-chip buffer amplifier(i.e., the gain may be 1). The state of the various switches 152, 154,158 may be controlled by on-chip or off-chip control circuitry (notshown).

While some components shown in FIGS. 1A and 1B are illustrated as beingexternal to the RF IC 102, in some embodiments, all of the elementsshown as external to the RF IC 102 or optionally external to the RF IC102 may be fully integrated onto a single IC die or onto a set ofintercoupled IC dies placed inside or embedded within a single ICpackage. A fully integrated version is to a great extent desirable,since all circuitry on the same die would have similar gradients forprocess, voltage, and temperature (PVT) variations, and hence acalibration scheme would be simplified.

FIG. 1C is a block diagram 170 of the multi-way switch complex 110 ofFIG. 1A, showing individually labeled switches 110 a-110 d, which may beimplemented, for example, as one or more FETs or MEMS devices. Adivider/switch 122 a, 122 b implemented as a set of switches may use a“half” version of the multi-way switch complex 110—for example, onlyswitches 110 b and 110 c. Optionally a set of switchable impedancematching elements may be included to accommodate the different number ofpaths enabled (e.g., switches 110 b and 110 c both closed, switches 110b and 110 c both open, or only one of switches 110 b and 110 c beingclosed with the other being open), and thus resulting impedanceperturbations. An example of such switchable impedance matching elementsis described below in conjunction with FIG. 3.

Referring back to FIG. 1A, by selectively controlling the multi-wayswitch complex 110 and the switches of one or more input/output circuits124, a signal originating in the transmit circuitry 104 can betransmitted as an RF signal through one or more phase-attenuation cores120 to one or more antennas 160 while isolating the receive circuitry116. Similarly, an RF signal received at one or more antennas 160 can beconveyed through one or more phase-attenuation cores 120 to the receivecircuitry 116 while isolating the transmit circuitry 104. In eithercase, the phase and/or amplitude of the RF signal may be modified by oneor more of the phase-attenuation cores 120. It should be understood thatFIG. 1A is simply one example of a transceiver RF system, and that otherconfigurations of transceiver RF systems are within the scope of theinvention as claimed below.

Referring back to FIG. 1A, in order to enable calibration of at leastthe phase-attenuation cores 120 of the illustrated RF IC 102, a set ofinternal switchable cross-circuit calibration (“C3”) paths 200, 202 areformed on-chip and connected between pairs of phase-attenuation cores120. As illustrated, C3 path 200 connects corresponding ports of Core 3and Core 4, and C3 path 202 connects corresponding ports of Core 1 andCore 2.

In the illustrated embodiment, C3 path 200 includes two associatedswitches 200 a, 200 b, and similarly C3 path 202 includes two associatedswitches 202 a, 202 b. Such a configuration is useful in conjunctionwith the embodiment shown in FIG. 3 described below, but only one switchper C3 path need be used if on-chip calibration is limited to thephase-attenuation cores 120. The associated C3 path switches may beimplemented, for example, as one or more FETs or MEMS devices.

FIG. 2 is a block diagram 250 showing a switch configuration for testingphase-attenuation Cores 1 and 2 of the RF IC of FIG. 1A. As illustrated,two of the switches (110 a, 110 c in FIG. 1C) of the multi-way switchcomplex 110 and the associated switches 202 a, 202 b of the C3 path 202are closed, thus creating a signal path as indicated by the bold dashedline—that is, from the transmit circuitry 104 through the buffer 106,image reject mixer 108, one signal path of the multi-way switch complex110, divider/switch 122 b, Core 2, C3 path 202, Core 1, divider/switch122 a, back through a different signal path of the multi-way switchcomplex 110, and thence through image reject mixer 112 and buffer 116 toreceive circuitry 116. All other illustrated switches are open. Thus, anRF signal from the transmit circuitry 104 can be conveyed internallythrough both Core 2 and Core 1 of the RF IC 102 to the receive circuitry116.

In a preferred embodiment, to calibrate Core 1, applied control signalsset Core 2 to have minimum amplitude adjustment and approximately zerophase shift to minimize any effect of Core 2 on an RF test signal (whichmay be just a normal RF transmission signal). At the same time, appliedcontrol signals set Core 3 and Core 4 to have a maximum attenuation(high impedance), primarily to provide a good 50 ohm impedance for thedivider/switches 122 a, 122 b, and secondarily to reduce the impact ofCore 3 and Core 4 on any measurements that may occur through RFcoupling. While an RF test signal (which may be varied over a desiredfrequency range) is applied by the transmit circuitry 104 and/or byexternal test equipment, applied control signals “sweep” (vary) theattenuation and/or phase state settings of Core 1 over a range ofpossible nominal settings at each applied RF signal frequency. Theactual effects on the internally conveyed RF signal of each nominalphase shift and attenuation state setting can be measured within thereceive circuitry 116 and/or by external test equipment.

Similarly, in a preferred embodiment, to calibrate Core 2, appliedcontrol signals set Core 1 to have minimum amplitude adjustment andapproximately zero phase shift, applied control signals optionally setCore 3 and Core 4 to have a maximum attenuation, and an RF test signal(which may be varied over a desired frequency range) is applied by thetransmit circuitry 104 and/or by external test equipment. Appliedcontrol signals sweep the attenuation and/or phase state settings ofCore 2 over a range of possible settings at each applied RF signalfrequency. The resulting effects on the internally conveyed RF signalcan be measured within the receive circuitry 116 and/or by external testequipment.

In both cases, the RF signal path is along the counter-clockwise bolddashed line 210 when characterizing the signal modification behavior ofCore 2 or Core 1. Note that a “clockwise” version of the RF signal paththat traverses through Core 1 first and Core 2 second can be achieved byreversing the illustrated switch states of the component switches of themulti-way switch complex 110. If desired, both the clockwise andcounter-clockwise versions of the RF signal path may be characterized;this may be advantageous if the Core blocks and/or signal paths areasymmetric. For example, Core 1 may have more amplitude controlvariation and phase shift range than Core 2, or the RF IC 102 maycontain an odd number of Cores (e.g., 3, 5, or 7).

In a similar manner, Cores 3 and 4 can be characterized by closing theother two switches (110 b, 110 d in FIG. 1C) of the multi-way switchcomplex 110, closing the associated switches 200 a, 200 b of the C3 path200, and opening all other illustrated switches, thus allowing an RFsignal to be conveyed from the transmit circuitry 104 internally throughCore 4 and then Core 3 of the RF IC 102 to the receive circuitry 116(i.e., counter-clockwise). Alternatively, an RF signal can be conveyedclockwise from the transmit circuitry 104 internally through Core 3 andthen Core 4 to the receive circuitry 116 by closing the associatedswitches 200 a, 200 b of the C3 path 200, but keeping the switchconfiguration of the multi-way switch complex 110 as shown in FIG. 2 andopening all other illustrated switches.

In tabular form, referring to the illustrated switches, an RF testsignal based on a signal originating from the transmit circuitry 104 canbe transmitted through any of the phase-attenuation cores 120 (Cores 1-4in this case) to the receive circuitry 116 by opening (binary 0) orclosing (binary 1) the switches as shown in TABLE 1:

TABLE 1 CORES TO TEST (order indicates direction of test signal) Core 2Core 1 Core 3 Core 4 SWITCH Core 1 Core 2 Core 4 Core 3 110a 1 0 1 0110b 0 1 0 1 110c 1 0 1 0 110d 0 1 0 1 200a 0 0 1 1 200b 0 0 1 1 202a 11 0 0 202b 1 1 0 0

Other calibration schemes may be used as well. For example, the testingscheme illustrated in FIG. 2 connects Cores 1 and 2 in series whileessentially isolating Cores 3 and 4. In alternative testing schemes, itmay be useful to serially connect more than two Cores, or to seriallyconnect two or more Cores in sets while concurrently connecting two ormore of such sets in parallel (some additional path switches may need tobe added in some cases). For example, referring to FIG. 2, switches 200a, 200 b of the C3 path 200 may be closed along with switches 202 a, 202b of the C3 path 202, thus creating a first signal path from thetransmit circuitry 104 through Cores 2 and 1 to the receive circuitry116, and a parallel second signal path from the transmit circuitry 104through Cores 3 and 4 to the receive circuitry 116. Such a parallelconfiguration allows characterization of the interaction of Cores 1 and4 over their respective ranges of attenuation and phase shift whileCores 2 and 3 are set to minimum amplitude adjustment and approximatelyzero phase shift. Similarly, the interaction of Cores 2 and 3 can becharacterized over their respective ranges of attenuation and phaseshift while Cores 1 and 4 are set to minimum amplitude adjustment andapproximately zero phase shift. In each case, the phase and/orattenuation settings for Cores being characterized may be varied inparallel across all such Cores, or one Core may be varied while one ormore other Cores are in a set phase/attenuation condition. Such testingof parallel sets of series connected Cores may provide insight into thebeam forming and path tapering characteristics of a particulartransceiver RF system embodied in or incorporating an RF IC 102.

Characterization of the phase-attenuation cores 120 (e.g., Cores 1-4) bymapping nominal phase and amplitude control states to actual phase shiftand amplitude (attenuation or amplification) levels may be sufficientfor some calibration purposes. For example, a nominal attenuation levelfor Core 1 of 1.5 dB may result in a measured attenuation level of 1.4dB. In some applications, simply knowing such discrepancies may bysufficient. In other cases, some designs for the phase-attenuation cores120 provide for internal compensation of such discrepancies, such as bystoring such mappings in a look-up table, so that the actual phase shiftand attenuation/amplification levels more closely correspond to thenominal phase and attenuation/amplification states. Examples of a phaseshifter circuit having extra circuity for enabling such compensationcapabilities may be found in U.S. patent application Ser. No.14/988,463, filed Jan. 5, 2016, entitled Reflection-Based RF PhaseShifter and assigned to the assignee of the present invention, theteachings of which are hereby incorporated by reference. Similarconsiderations apply to adding and utilizing extra attenuation oramplifier elements for compensation purposes within the attenuatorportion of a phase-attenuation core 120. In all cases, it is useful tocharacterize all of the phase-attenuation cores 120 (Cores 1-4 in theexample of FIG. 2) to take into account possible variations between suchcores, for example, due to process variations and differences inadjacent circuitry.

Core Circuit+Input/Output Circuit Testing Configuration

The concepts described above can be extended to include more circuitrythat may affect an RF signal conveyed to or from the antennas 160. Thus,while the embodiment of FIG. 1A and FIG. 2 allows for characterizationof the phase-attenuation cores 120, it is possible to extend testing tomore peripheral circuitry in the RF IC 102, such as the on-chipamplifiers 154 a, 156 b (see FIG. 1B) in each associated input/outputcircuit 124. For example, FIG. 3 is a block diagram of a secondembodiment of an RF IC with integrated calibration circuitry suitablefor use in a transceiver RF system. Formed on-chip with the circuit ofFIG. 1A are sets of internal switchable periphery cross-circuitcalibration (“PC3”) paths 302, 304, each connected to the transmit pathTX and the receive path RX of pairs of phase-attenuation cores 120 byassociated switches 302 a-302 d, 304 a-304 d. (Note that the PC3 pathsare essentially the same as C3 paths, differing only in the connectionpoints and number of switches, and are re-named only for clarity in thefollowing description.)

As illustrated, PC3 path 302 connects corresponding TX and RX paths ofCore 3 and Core 4, and PC3 path 304 connects corresponding TX and RXpaths of Core 1 and Core 2, at a point “between” corresponding on-chipamplifiers 154 a, 156 b (see FIG. 1B) and external circuit connectionsfor the RF IC 102. Each PC3 path 302, 304 is also coupled by anassociated link switch 302 e, 304 e to a corresponding C3 path 200, 202.The associated PC3 path and link switches may be implemented, forexample, as one or more FETs or MEMS devices.

By setting the states of the multi-way switch complex 110, the switchesof an associated input/output circuit 124, the switches 302 a-302 e, 304a-304 e associated with the PC3 paths 302, 304, and the switches 200a-200 b, 202 a-202 b of the C3 paths 200, 202, an RF test signal fromthe transmit circuitry 104 can be transmitted through any of thephase-attenuation cores 120 (Cores 1-4 in this case), through either anassociated output amplifier 154 a or input amplifier 156 b, and then tothe receive circuitry 116. Accordingly, the characteristics of any oneamplifier 154 a, 156 b in the chain of components can be determined.

For example, referring to FIG. 3, the influence of the output amplifier154 a for Core 2 can be characterized by closing switch 110 c (see FIG.1C), SPST switch 152 (see FIG. 1B), switch 304 c, link switch 304 e,switch 202 a, and switch 110 a, while opening all other illustratedswitches. Similarly, the influence of the input amplifier 156 b for Core1 can be characterized by closing switch 110 c, switch 202 b, linkswitch 304 e, switch 304 a, SPST switch 154, and switch 110 a, whileopening all other illustrated switches.

Focusing on just Cores 1 and 2, at least the peripheral component testsignal pathways shown in TABLE 2 can be achieved by opening (binary 0)or closing (binary 1) the specified switches (note that these are inaddition to the available test pathways shown in TABLE 1). All otherillustrated switches not shown in TABLE 2 should be open. A similar setof switch settings will apply to Cores 3 and 4, or to any other numberof phase-attenuation cores 120.

TABLE 2 SIGNAL PATHS TO TEST Core 1 Core 1 Core 2 Core 2 SWITCH TX ampRX amp TX amp RX amp 110a 0 1 1 0 110b 1 0 0 1 110c 0 1 1 0 110d 1 0 0 1202a 0 0 1 1 202b 1 1 0 0 304a 0 1 0 0 304b 1 0 0 0 304c 0 0 1 0 304d 00 0 1 304e 1 1 1 1 Core 1 TX: 152 1 0 0 0 Core 1 RX: 154 0 1 0 0 Core 2TX: 152 0 0 1 0 Core 2 RX: 154 0 0 0 1

As in the case of characterizing the phase-attenuation cores 120,mapping nominal phase and amplitude control states to actual phase shiftand attenuation/amplification levels for each phase-attenuation core 120as influenced by the associated amplifiers 154 a, 154 b may besufficient for some calibration purposes. In other cases, some designsfor the phase-attenuation cores 120 provide for internal compensation ofsuch discrepancies, so that the actual phase shift andattenuation/amplification levels can be set to more closely correspondto the nominal phase and attenuation/amplification states.

In some testing configurations, impedance mismatches may occur due toasymmetric loading of the divider/switches 122 a, 122 b as an RF testsignal is routed to only one set of cores (e.g., Core 1 and Core 2)while other sets of cores (e.g., Core 3 and Core 4) are set to be in anessentially disconnected or isolated state. To counteract suchmismatches, offsetting impedances 310 a, 310 b (shown as absorptiveshunt resistors, by way of example) optionally may be coupled byassociated switches 312 a, 312 b to the switch complex 110 at the portscoupled to the image reject mixers 108, 110. While only two suchoffsetting impedances 310 a, 310 b are shown (on the “bottom” side ofthe switch complex 110), for layout symmetry, it may be desirable toprovide similar switched impedances on the “top” side of the switchcomplex 110. The associated switches may be implemented, for example, asone or more FETs or MEMS devices.

For an RF IC 102 for circuitry having a characteristic impedance of 50ohms, the offsetting impedances 310 a, 310 b may be about 100 ohms each.In operation, when a calibration mode RF test path is created within theRF IC 102 through the C3 paths 200, 202 and/or the PC3 paths 302, 304,the switches 312 a, 312 b associated with the offsetting impedances 310a, 310 b would be closed. In a normal, non-calibration operational mode,the switches 312 a, 312 b associated with the offsetting impedances 310a, 310 b would be open.

Similarly, a set of switchable impedance matching elements may beincluded in the divider/switches 122 a, 122 b themselves to accommodatethe different number of paths enabled, and thus resulting impedanceperturbations.

Internal Circuit Testing Configuration

Another optional circuit that may be included in embodiments of theinvention is a switch that allows connection of the intermediatefrequency (IF) portion of the end-to-end transmit circuitry 104 signalpath to the IF portion of the receive circuitry 116, either directly orindirectly (i.e., with intermediate RF up-mixing and down-mixing). TheIF portion of the end-to-end signal path is typically at a significantlylower frequency than the “over the air” transmitted and received signalsfor such a system. For example, while the “over the air” frequency maybe around 30 GHz, the corresponding IF frequency may be about 3-4 GHz.Testing at IF frequencies has an advantage because less expensivetesting equipment is required and influences by the testing environment(e.g., parasitic coupling) are lessened.

FIG. 4A is a block diagram of a portion of the circuitry of FIG. 1A orFIG. 3 showing an indirect intermediate frequency path bypass switch402. As illustrated, the indirect IF bypass switch 402 is coupledbetween the transmitter image reject mixer 108 (which up-converts IFsignals to RF signals) and the receiver image reject mixer 110 (whichdown-converts RF signals to IF signals). The indirect IF bypass switch402 may be implemented, for example, as one or more FETs or MEMSdevices. In operation, by closing the indirect IF bypass switch 402while setting all of the switches 110 a-110 d of the switch complex 110open, the transmit circuitry 104 is coupled to the receive circuitry 116through the image reject mixers 108, 110. Such a test configurationallows characterization of the end-to-end circuit path from the transmitcircuitry 104 to the receive circuitry 116 with a minimum of influencefrom other circuitry on the RF IC 102 (e.g., the divider/switches 122 a,122 b and the Cores 1-4).

FIG. 4B is a block diagram of a portion of the circuitry of FIG. 1A orFIG. 3 showing a direct IF bypass switch 404. As illustrated, the directIF bypass switch 404 is coupled between the transmit signal path buffer106 and the receive signal path buffer 114 (but may be coupled to anypart of the respective IF signal paths). The direct IF bypass switch 404may be implemented, for example, as one or more FETs or MEMS devices. Inoperation, by closing the direct IF bypass switch 404 while setting allof the switches 110 a-110 d of the switch complex 110 open, an IF signalfrom the transmit circuitry 104 is directly coupled to the IF signalpath of the receive circuitry 116. Such a test configuration allowscharacterization of the end-to-end circuit path from the transmitcircuitry 104 to the receive circuitry 116 with a minimum of influencefrom other circuitry on the RF IC 102, including influences from theimage reject mixers 108, 112.

As shown in FIG. 4B, both an indirect IF bypass switch 402 and a directIF bypass switch 404 may be included on an RF IC 102 to allowcharacterization of the end-to-end circuit path from the transmitcircuitry 104 to the receive circuitry 116 with or without the imagereject mixers 108, 112 in the circuit path.

Using an indirect IF bypass switch 402 and/or a direct IF bypass switch404 to characterize all or part of the end-to-end signal circuit pathalone may be useful to “de-embed” the IF path characteristics from theactual RF measurements that are needed for calibration of the Cores(i.e., essentially allowing the effects of the IF components determinedduring a first calibration mode pass to be subtracted from the RFmeasurements through at least one Core during a second calibration modepass). This may be particularly important for frequency variation acrossthe RF bandwidth of interest because such variation is a much largerproportion of the total bandwidth at the lower IF frequency than it isat the higher RF frequency—for example, a frequency sweep of 2 GHzcentered at an IF frequency of 4 GHz will show much more performancevariation than a frequency sweep of 2 GHz centered at an RF frequency of28 GHz.

As noted above, more than or fewer than four transceiver front-endcircuits (i.e., phase-attenuation cores 120, optionally with associatedinput/output circuits 124) may be included on the RF IC 102. For two orfour transceiver front-end circuits, the switchable cross-circuitcalibration paths and switchable periphery cross-circuit calibrationpaths can be configured as shown in FIG. 1A and/or FIG. 3. For more thanfour transceiver front-end circuits on an RF IC 102, the switchablecross-circuit calibration paths, switchable periphery cross-circuitcalibration paths, and various switch states can be configured in avariety of ways so long as each element of the transceiver front-endcircuits to be tested (e.g., phase-attenuation cores 120 and/or on-chipamplifiers 154 a, 156 b) can be coupled to an RF test signal andmeasurement circuitry or devices in relative isolation from otherelements of the RF IC 102.

Single Core Circuit Testing Configuration

The concepts described above can be extended to include less circuitrythat may affect an RF signal conveyed to or from the antennas 160. Forexample, FIG. 5 is a block diagram of a third embodiment of an RF ICwith integrated calibration circuitry suitable for use in a transceiverRF system. Formed on-chip with the circuit of FIG. 1A are sets ofinternal switchable bypass circuit calibration (“BC2”) paths 502, 504,each connected to the reception path Rx by associated switches 502 a-502b, 504 a-504 b. (Note that the BC2 paths are essentially the same as C3or PC3 paths, differing only in the connection points and number ofswitches, and are re-named only for clarity in the followingdescription.)

As illustrated, BC2 path 502 connects to Core 2 through switch 502 a,and to Core 3 through switch 502 b. Similarly, BC2 path 504 connects toCore 1 through switch 504 a, and to Core 4 through switch 504 b. Theassociated BC2 path switches may be implemented, for example, as one ormore FETs or MEMS devices.

By setting the states of the multi-way switch complex 110 and theswitches 502 a-502 b, 504 a-504 b associated with the BC2 paths 502,504, an RF test signal from the transmit circuitry 104 can betransmitted through one of the phase-attenuation cores 120 (Cores 1-4 inthis case) back to the receive circuitry 116 without the signaltraversing any other phase-attenuation core 120. Accordingly, thecharacteristics of one phase-attenuation core 120 can be measuredwithout the direct influence of any other phase-attenuation core 120(ignoring possible parasitic couplings from nearby placement on the RFIC 102 of such other cores).

For example, referring to FIG. 5, Core 2 can be characterized by closingswitch 110 c (see FIG. 1C) and switch 502 a while opening all otherillustrated switches, thus creating a signal path as indicated by thebold dashed line—that is, from the transmit circuitry 104 through thebuffer 106, image reject mixer 108, one signal path of the multi-wayswitch complex 110, divider/switch 122 b, Core 2, switch 502 a, BC2 path502, and thence through image reject mixer 112 and buffer 116 to receivecircuitry 116. Thus, an RF signal from the transmit circuitry 104 can beconveyed internally through only Core 2 of the RF IC 102 to the receivecircuitry 116. Similarly, Core 3 alone can be characterized by closingswitch 110 c and switch 502 b while opening all other illustratedswitches, Core 1 alone can be characterized by closing switch 110 d andswitch 504 a while opening all other illustrated switches, and Core 4alone can be characterized by closing switch 110 d and switch 504 bwhile opening all other illustrated switches.

As illustrated, BC2 path 502 connects to Core 2 through switch 502 a ata node 506. In an alternative embodiment, switch 502 a may instead becoupled (as suggested by the dotted line) to a node 508 as a switchablebypass periphery circuit calibration (“BPC2”) path (with similarconnections for the other Cores if desired). By setting the states ofthe multi-way switch complex 110, switch 502 a associated with the BPC2path 502, and switch 152 in the associated input/output circuit 124,while opening all other illustrated switches, an RF test signal from thetransmit circuitry 104 can be conveyed through Core 1, through theassociated output amplifier 154 a, and then directly to the receivecircuitry 116. Accordingly, the characteristics of the associatedamplifier 154 a in the chain of components of Core 1 can be determinedwithout the test signal traversing any other Cores, thus testing onlyone Core at a time. As should be clear, by adding switches, embodimentsmay include both BC2 and BPC2 calibration paths for any of the Cores, aswell as cross-circuit calibration (“C3”) paths and/or peripherycross-circuit calibration (“PC3”) paths, as in FIG. 3. In a similarmanner, by adding switches, any circuit component can be bypassed toremove it from a measurement.

Benefits

One usage of the inventive concepts is periodic self-calibration of anRF IC 102 by characterizing the performance of the variousphase-attenuation core circuits, periphery amplifier circuits, and thecircuit components within the end-to-end IF signal path, and thenadjusting one or more of such circuits to tune for one or more desiredperformance parameters (e.g., bandwidth, insertion loss, linearity,etc.). It is thus possible to apply a pseudo closed-loop calibrationmechanism from time to time.

Embodiments of the invention include one or more on-chip switchableinternal calibration paths that enable direct coupling of atransmit-to-receive signal path of the on-chip circuit to an RF testsystem while isolating other circuitry on the chip. Advantages ofvarious embodiments of the invention include a calibration architecturethat enables accurate calibration of RF ICs used in transceiver RFsystems in a relatively simple testing environment that is done bydirect connection (as opposed to “over the air”) at significantly lowerfrequencies. Accordingly, environmental factors in the test set-up thatalter, shield, attenuate, distort, or otherwise affect transmitted andreceived “over the air” test signals are eliminated or significantlymitigated. Further, periodic self-calibration of an RF IC in accordancewith the present invention can be performed after initial factorycalibration, so that adjustments in desired performance parameters(e.g., bandwidth, insertion loss, linearity, etc.) can be made whilesuch an IC is embedded within a final system, and thus take into accountthe actual usage environment (including, for example, temperature,electrically “noisy” circuitry, parasitic electromagnetic coupling,etc.). Periodic self-calibration also allows re-characterization of suchan RF IC to take into account component degradation due to age or otherfactors. It is thus possible to apply a pseudo closed-loop calibrationmechanism from time to time.

Note also that it is possible to do the testing as part of anover-the-air transmission where all paths to connected antennas 160would transmit as normal except for one path being tested (e.g., throughan associated Core and/or part of an associated input/output circuit124). The path being tested would be disconnected from its associatedantenna and at least the associated core would be evaluated. In such acase, the “RF test signal” may be just a normal RF transmission signal.

It should also be noted that while the above description andaccompanying figures are directed to a transceiver RF system configuredfor a time division duplex (TDD) communication protocol, the sameconcepts may be applied to a transceiver RF system configured for afrequency division duplex (FDD) communication protocol or for othertypes of communication protocols employing one or more transceivers.

Methods

Another aspect of the invention includes methods for calibrating a radiofrequency (RF) integrated circuit. FIG. 6 is a flowchart 600 showing afirst method for calibrating a radio frequency (RF) integrated circuit,including: providing a primary RF transmission path (STEP 602);providing a primary RF reception path (STEP 604); selectively connectingat least one RF transceiver front-end circuit to the primary RFtransmission path and the primary RF reception path (STEP 606); couplingat least one switchable internal calibration path [e.g., a cross-circuitcalibration (C3) or periphery cross-circuit calibration (PC3) or bypasscircuit calibration (BC2) or bypass periphery circuit calibration (BPC2)path] to the at least one RF transceiver front-end circuit (STEP 608);and configuring the at least one switchable internal calibration path toconvey, in a calibration mode, an RF test signal from the primary RFtransmission path through at least a portion of the coupled at least oneRF transceiver front-end circuit to the primary RF reception path (STEP610).

Other aspects of the above method include: minimizing the effects on theRF test signal of all but one of the coupled at least one RF transceiverfront-end circuit so as to relatively isolate any remaining coupled RFtransceiver front-end circuits; at least one RF transceiver front-endcircuit being a phase-attenuation core; each RF transceiver front-endcircuit being a phase-attenuation core; at least one RF transceiverfront-end circuit being an input/output circuit; each RF transceiverfront-end circuit being an input/output circuit; providing a direct orindirect intermediate frequency path bypass switch coupled between theprimary RF transmission path and the primary RF reception path, andselectively coupling the RF test signal from the primary RF transmissionpath to the primary RF reception path; and providing one or moreoffsetting impedances selectably connectable to at least one of theprimary RF transmission path or primary RF reception path, andconnecting the one or more offsetting impedances to at least one of theprimary RF transmission path or primary RF reception path during thecalibration mode.

Yet another aspect of the invention includes a method for calibrating aradio frequency (RF) integrated circuit, including: providing a primaryRF transmission path; providing a primary RF reception path; providingat least two RF transceiver front-end circuits each selectivelyconnectable to the primary RF transmission path and the primary RFreception path, each RF transceiver front-end circuit including aphase-attenuation core and an associated input/output circuit; providingat least one switchable internal calibration path coupled to the atleast two RF transceiver front-end circuits; configuring the at leastone switchable internal calibration path to convey, in a calibrationmode, an RF test signal from the primary RF transmission path through atleast a portion of the coupled at least two RF transceiver front-endcircuits to the primary RF reception path; and during the calibrationmode, minimizing the effects on the RF test signal of all but one of thecoupled at least two RF transceiver front-end circuits so as torelatively isolate the remaining coupled RF transceiver front-endcircuit.

Other aspects of the above method include: providing a direct orindirect intermediate frequency path bypass switch coupled between theprimary RF transmission path and the primary RF reception path, andselectively coupling the RF test signal from the primary RF transmissionpath to the primary RF reception path; providing one or more offsettingimpedances selectably connectable to at least one of the primary RFtransmission path or primary RF reception path, and connecting the oneor more offsetting impedances to at least one of the primary RFtransmission path or primary RF reception path during the calibrationmode; and providing at least a first and a second switchable internalcalibration paths, the at least first switchable internal calibrationpath being selectively connectable to the phase-attenuation cores ofeach of the at least two RF transceiver front-end circuits, and the atleast second switchable internal calibration path being selectivelyconnectable to the associated input/output circuit of each of the atleast two RF transceiver front-end circuits.

Further aspects of the above methods include: at least one RFtransceiver front-end circuit including at least one of aphase-attenuation core or an input/output circuit; each RF transceiverfront-end circuit including a phase-attenuation core; each RFtransceiver front-end circuit including an input/output circuit; atleast one RF transceiver front-end circuit including an input/outputcircuit that includes at least one of a power amplifier and/or a lownoise amplifier; coupling an indirect intermediate frequency (IF) pathbypass switch between an IF portion of the primary RF transmission pathand an IF portion of the primary RF reception path, and selectivelycoupling the RF test signal from the primary RF transmission path to theprimary RF reception path; adjusting desired performance parameters ofthe RF integrated circuit based on the results of the calibration mode;performing a first calibration mode pass through the indirect IF pathbypass switch, performing a second calibration mode pass through atleast one RF transceiver front-end circuit, and subtracting the resultsof the first calibration mode pass from the results of the secondcalibration mode pass; coupling a direct intermediate frequency (IF)path bypass switch between an IF portion of the primary RF transmissionpath and an IF portion of the primary RF reception path, and selectivelycoupling the RF test signal from the primary RF transmission path to theprimary RF reception path; adjusting desired performance parameters ofthe RF integrated circuit based on the results of the calibration;performing a first calibration mode pass through the direct IF pathbypass switch, performing a second calibration mode pass through atleast one RF transceiver front-end circuit, and subtracting the resultsof the first calibration mode pass from the results of the secondcalibration mode pass; selectably connecting one or more offsettingimpedances to at least one of the primary RF transmission path orprimary RF reception path to offset impedance mismatches due toasymmetric loading of one or more switchable internal calibration pathsduring the calibration mode; at least one phase-attenuation coreincluding a signal amplitude control circuit that includes an attenuatorcircuit for providing a reduction in amplitude of an applied signal; atleast one phase-attenuation core including a signal amplitude controlcircuit that includes an amplifier that amplifies an applied signal toeffectively provide negative attenuation; at least one switchableinternal calibration path being a switchable cross-circuit calibrationpath between at least two RF transceiver front-end circuits and theprimary RF reception path and configured for conveying, in thecalibration mode, the RF test signal from the primary RF transmissionpath through such at least two RF transceiver front-end circuits to theprimary RF reception path; at least one RF transceiver front-end circuitincluding an input/output circuit, and wherein at least one switchablecross-circuit calibration path is a periphery cross-circuit calibrationpath configured for conveying, in the calibration mode, the RF testsignal from the primary RF transmission path through at least a portionof such input/output circuit of such at least one RF transceiverfront-end circuit to the primary RF reception path; at least oneswitchable internal calibration path being a switchable bypass circuitcalibration path between at least one RF transceiver front-end circuitand the primary RF reception path and configured for conveying, in thecalibration mode, the RF test signal from the primary RF transmissionpath through such at least one RF transceiver front-end circuit directlyto the primary RF reception path; at least one RF transceiver front-endcircuit including an input/output circuit, and wherein at least oneswitchable bypass circuit calibration path is a bypass periphery circuitcalibration path configured for conveying, in the calibration mode, theRF test signal from the primary RF transmission path through at least aportion of such input/output circuit of such at least one RF transceiverfront-end circuit directly to the primary RF reception path; minimizingthe effects on the RF test signal of all but one of the coupled at leastone RF transceiver front-end circuit so as to relatively isolate anyremaining coupled RF transceiver front-end circuits; minimizing theeffects on the RF test signal by RF transceiver front-end circuits notbeing calibrated but conveying the RF test signal, by configuring suchRF transceiver front-end circuits to a minimum amplitude adjustmentand/or approximately zero phase shift; minimizing the effects on the RFtest signal by RF transceiver front-end circuits not conveying the RFtest signal, by configuring such RF transceiver front-end circuits tomaximum attenuation; minimizing the effects on the RF test signal by RFtransceiver front-end circuits not conveying the RF test signal, byconfiguring each switchable internal calibration path coupled to such RFtransceiver front-end circuits to an open state; coupling a switchabletermination circuit to the at least one RF transceiver front-end, andminimizing the effects on the RF test signal by such RF transceiverfront-end circuits not conveying the RF test signal, by configuring suchswitchable termination circuits to a shunt mode; minimizing the effectson the RF test signal by RF transceiver front-end circuits not beingcalibrated but conveying the RF test signal, by configuring such RFtransceiver front-end circuits to a minimum amplitude adjustment and/orapproximately zero phase shift, and minimizing the effects on the RFtest signal by RF transceiver front-end circuits not conveying the RFtest signal, by configuring such RF transceiver front-end circuits tomaximum attenuation and by configuring each switchable internalcalibration path coupled to such RF transceiver front-end circuits to anopen state; conveying the RF test signal through at least two RFtransceiver front-end circuits; concurrently conveying the RF testsignal through at least two parallel sets of at least oneserially-connected RF transceiver front-end circuit; performing aninitial calibration mode when the RF integrated circuit is manufactured;adjusting desired performance parameters of the RF integrated circuitbased on the results of the calibration mode; mapping nominal phase andamplitude control states to actual phase shift and amplitude levelsdetermined during the calibration mode; varying the RF test signal overa desired frequency range; and/or performing the calibration modeperiodically after the RF integrated circuit is manufactured to takeinto account an actual usage environment, which may include temperature.

Fabrication Technologies and Options

To further minimize any effect on calibration characterization, Coresthat do not convey an RF test signal can also be coupled at variouspoints to switchable termination circuitry. For example, referring toFIG. 5, terminating shunt switches (not shown) to circuit ground (orother reference potential) can be positioned at nodes 510 betweenassociated Cores 120 and their associated divider/switch 122 a, 122 b. Aterminating shunt switch would have essentially no effect on theassociated node 510 when the switch is open, and would connects atermination impedance (such as 50 ohms) to circuit ground (or otherreference potential) when the switch is closed. Terminating shuntswitches may be implemented, for example, as one or more FETs or MEMSdevices. A shunt switch can be set to a shunt mode in which theconnecting node to an associated Core is coupled to circuit ground. Asshould be clear, embodiments may include such switchable terminationcircuitry at other positions with respect to the Cores, such as betweeneach Core and its associated input/output circuit 124. As anotherexample of isolation, bias voltages to any active devices (e.g., FETs)within the Cores that do not convey an RF test signal can be set to anOFF state.

The term “MOSFET”, as used in this disclosure, means any field effecttransistor (FET) with an insulated gate and comprising a metal ormetal-like, insulator, and semiconductor structure. The terms “metal” or“metal-like” include at least one electrically conductive material (suchas aluminum, copper, or other metal, or highly doped polysilicon,graphene, or other electrical conductor), “insulator” includes at leastone insulating material (such as silicon oxide or other dielectricmaterial), and “semiconductor” includes at least one semiconductormaterial.

As should be readily apparent to one of ordinary skill in the art,various embodiments of the invention can be implemented to meet a widevariety of specifications. Unless otherwise noted above, selection ofsuitable component values is a matter of design choice and variousembodiments of the invention may be implemented in any suitable ICtechnology (including but not limited to MOSFET and IGFET structures),or in hybrid or discrete circuit forms. Integrated circuit embodimentsmay be fabricated using any suitable substrates and processes, includingbut not limited to standard bulk silicon, silicon-on-insulator (SOI),silicon-on-sapphire (SOS), GaN HEMT, GaAs pHEMT, and MESFETtechnologies. However, the inventive concepts described above areparticularly useful with an SOI-based fabrication process (includingSOS), and with fabrication processes having similar characteristics.Fabrication in CMOS on SOI or SOS enables low power consumption, goodisolation in the non-conducting OFF state to avoid leakage of signalsinto other circuitry, the ability to withstand high power signals duringoperation due to FET stacking, good linearity, and high frequencyoperation (in excess of about 10 GHz, and particularly above about 20GHz). Monolithic IC implementation is particularly useful sinceparasitic capacitances generally can be kept low (or at a minimum, keptuniform across all units, permitting them to be compensated) by carefuldesign.

Voltage levels may be adjusted or voltage and/or logic signal polaritiesreversed depending on a particular specification and/or implementingtechnology (e.g., NMOS, PMOS, or CMOS, and enhancement mode or depletionmode transistor devices). Component voltage, current, and power handlingcapabilities may be adapted as needed, for example, by adjusting devicesizes, serially “stacking” components (particularly FETs) to withstandgreater voltages, and/or using multiple components in parallel to handlegreater currents. Additional circuit components may be added to enhancethe capabilities of the disclosed circuits and/or to provide additionalfunctional without significantly altering the functionality of thedisclosed circuits.

A number of embodiments of the invention have been described. It is tobe understood that various modifications may be made without departingfrom the spirit and scope of the invention. For example, some of thesteps described above may be order independent, and thus can beperformed in an order different from that described. Further, some ofthe steps described above may be optional. Various activities describedwith respect to the methods identified above can be executed inrepetitive, serial, or parallel fashion.

It is to be understood that the foregoing description is intended toillustrate and not to limit the scope of the invention, which is definedby the scope of the following claims, and that other embodiments arewithin the scope of the claims. (Note that the parenthetical labels forclaim elements are for ease of referring to such elements, and do not inthemselves indicate a particular required ordering or enumeration ofelements; further, such labels may be reused in dependent claims asreferences to additional elements without being regarding as starting aconflicting labeling sequence).

What is claimed is:
 1. A radio frequency (RF) integrated circuitincluding: (a) a primary RF transmission path; (b) a primary RFreception path; (c) at least one RF transceiver front-end circuit, eachselectively connectable to the primary RF transmission path and theprimary RF reception path; and (d) at least one switchable internalcalibration path coupled to the at least one RF transceiver front-endcircuit and configured to convey, in a calibration mode, an RF testsignal from the primary RF transmission path through at least a portionof the coupled at least one RF transceiver front-end circuit to theprimary RF reception path; wherein at least one RF transceiver front-endcircuit includes at least one of a phase-attenuation core or aninput/output circuit.
 2. The invention of claim 1, wherein each RFtransceiver front-end circuit includes a phase-attenuation core.
 3. Theinvention of claim 1, wherein each RF transceiver front-end circuitincludes an input/output circuit.
 4. The invention of claim 1, whereinat least one RF transceiver front-end circuit includes an input/outputcircuit that includes at least one of a power amplifier and/or a lownoise amplifier.
 5. The invention of claim 1, further including anindirect intermediate frequency (IF) path bypass switch coupling an IFportion of the primary RF transmission path and an IF portion of theprimary RF reception path, for selectively coupling the RF test signalfrom the primary RF transmission path to the primary RF reception path.6. The invention of claim 5, wherein adjustments in desired performanceparameters are made to the RF integrated circuit based on the results ofthe calibration mode.
 7. The invention of claim 5, wherein a firstcalibration mode pass is performed through the indirect IF path bypassswitch, and a second calibration mode pass is performed through at leastone RF transceiver front-end circuit, and the results of the firstcalibration mode pass are subtracted from the results of the secondcalibration mode pass.
 8. The invention of claim 1, further including adirect intermediate frequency (IF) path bypass switch coupled between anIF portion of the primary RF transmission path and an IF portion of theprimary RF reception path, for selectively coupling the RF test signalfrom the primary RF transmission path to the primary RF reception path.9. The invention of claim 8, wherein adjustments in desired performanceparameters are made to the RF integrated circuit based on the results ofthe calibration mode.
 10. The invention of claim 8, wherein a firstcalibration mode pass is performed through the direct IF path bypassswitch, and a second calibration mode pass is performed through at leastone RF transceiver front-end circuit, and the results of the firstcalibration mode pass are subtracted from the results of the secondcalibration mode pass.
 11. The invention of claim 1, further includingone or more offsetting impedances selectably connectable to at least oneof the primary RF transmission path or primary RF reception path tooffset impedance mismatches due to asymmetric loading of one or moreswitchable internal calibration paths during the calibration mode. 12.The invention of claim 1, wherein at least one phase-attenuation coreincludes a signal amplitude control circuit that includes an attenuatorcircuit for providing a reduction in amplitude of an applied signal. 13.The invention of claim 1, wherein at least one phase-attenuation coreincludes a signal amplitude control circuit that includes a n amplifierthat amplifies an applied signal to effectively provide negativeattenuation.
 14. The invention of claim 1, wherein at least oneswitchable internal calibration path is a switchable cross-circuitcalibration path between at least two RF transceiver front-end circuitsand the primary RF reception path and configured to convey, in thecalibration mode, the RF test signal from the primary RF transmissionpath through such at least two RF transceiver front-end circuits to theprimary RF reception path.
 15. The invention of claim 14, wherein atleast one RF transceiver front-end circuit includes an input/outputcircuit, and wherein at least one switchable cross-circuit calibrationpath is a periphery cross-circuit calibration path configured to convey,in the calibration mode, the RF test signal from the primary RFtransmission path through at least a portion of such input/outputcircuit of such at least one RF transceiver front-end circuit to theprimary RF reception path.
 16. The invention of claim 1, wherein atleast one switchable internal calibration path is a switchable bypasscircuit calibration path between at least one RF transceiver front-endcircuit and the primary RF reception path and configured to convey, inthe calibration mode, the RF test signal from the primary RFtransmission path through such at least one RF transceiver front-endcircuit directly to the primary RF reception path.
 17. The invention ofclaim 16, wherein at least one RF transceiver front-end circuit includesan input/output circuit, and wherein at least one switchable bypasscircuit calibration path is a bypass periphery circuit calibration pathconfigured to convey, in the calibration mode, the RF test signal fromthe primary RF transmission path through at least a portion of suchinput/output circuit of such at least one RF transceiver front-endcircuit directly to the primary RF reception path.
 18. The invention ofclaim 1, wherein the effects on the RF test signal of all but one of thecoupled at least one RF transceiver front-end circuit are minimized soas to relatively isolate any remaining coupled RF transceiver front-endcircuits.
 19. The invention of claim 1, wherein the effects on the RFtest signal by RF transceiver front-end circuits not being calibratedbut conveying the RF test signal are minimized by configuring such RFtransceiver front-end circuits to a minimum amplitude adjustment. 20.The invention of claim 1, wherein the effects on the RF test signal byRF transceiver front-end circuits not conveying the RF test signal areminimized by configuring such RF transceiver front-end circuits tomaximum attenuation.
 21. The invention of claim 1, wherein the effectson the RF test signal by RF transceiver front-end circuits not conveyingthe RF test signal are minimized by configuring each switchable internalcalibration path coupled to such RF transceiver front-end circuits to anopen state.
 22. The invention of claim 1, wherein the at least one RFtransceiver front-end includes a switchable termination circuit, andwherein the effects on the RF test signal by such RF transceiverfront-end circuits not conveying the RF test signal are minimized byconfiguring such switchable termination circuits to a shunt mode. 23.The invention of claim 1, wherein the effects on the RF test signal byRF transceiver front-end circuits not being calibrated but conveying theRF test signal are minimized by configuring such RF transceiverfront-end circuits to a minimum amplitude adjustment and approximatelyzero phase shift, and wherein the effects on the RF test signal by RFtransceiver front-end circuits not conveying the RF test signal areminimized by configuring such RF transceiver front-end circuits tomaximum attenuation and by configuring each switchable internalcalibration path coupled to such RF transceiver front-end circuits to anopen state.
 24. The invention of claim 1, wherein the RF test signal isconveyed through at least two RF transceiver front-end circuits.
 25. Theinvention of claim 1, wherein the RF test signal is concurrentlyconveyed through at least two parallel sets of at least oneserially-connected RF transceiver front-end circuit.
 26. The inventionof claim 1, wherein an initial calibration mode is performed when the RFintegrated circuit is manufactured.
 27. The invention of claim 1,wherein the calibration mode is performed periodically after the RFintegrated circuit is manufactured.
 28. The invention of claim 1,wherein adjustments in desired performance parameters are made to the RFintegrated circuit based on the results of the calibration mode.
 29. Theinvention of claim 1, wherein the calibration mode results in a mappingof nominal phase and amplitude control states to actual phase shift andamplitude levels.
 30. A method for calibrating a radio frequency (RF)integrated circuit, including: (a) providing a primary RF transmissionpath; (b) providing a primary RF reception path; (c) selectivelyconnecting at least one RF transceiver front-end circuit to the primaryRF transmission path and the primary RF reception path; (d) coupling atleast one switchable internal calibration path to the at least one RFtransceiver front-end circuit; and (e) configuring the at least oneswitchable internal calibration path to convey, in a calibration mode,an RF test signal from the primary RF transmission path through at leasta portion of the coupled at least one RF transceiver front-end circuitto the primary RF reception path; wherein at least one RF transceiverfront-end circuit includes at least one of a phase-attenuation core oran input/output circuit.
 31. The method of claim 30, wherein each RFtransceiver front-end circuit includes a phase-attenuation core.
 32. Themethod of claim 30, wherein each RF transceiver front-end circuitincludes an input/output circuit.
 33. The method of claim 30, wherein atleast one RF transceiver front-end circuit includes an input/outputcircuit that includes at least one of a power amplifier and/or a lownoise amplifier.
 34. The method of claim 30, further including: (a)coupling an indirect intermediate frequency (IF) path bypass switchbetween an IF portion of the primary RF transmission path and an IFportion of the primary RF reception path; and (b) selectively couplingthe RF test signal from the primary RF transmission path to the primaryRF reception path.
 35. The method of claim 34, further includingadjusting desired performance parameters of the RF integrated circuitbased on the results of the calibration mode.
 36. The method of claim34, further including: (a) performing a first calibration mode passthrough the indirect IF path bypass switch; (b) performing a secondcalibration mode pass through at least one RF transceiver front-endcircuit; and (c) subtracting the results of the first calibration modepass from the results of the second calibration mode pass.
 37. Themethod of claim 30, further including: (a) coupling a directintermediate frequency (IF) path bypass switch between an IF portion ofthe primary RF transmission path and an IF portion of the primary RFreception path; and (b) selectively coupling the RF test signal from theprimary RF transmission path to the primary RF reception path.
 38. Themethod of claim 37, further including adjusting desired performanceparameters of the RF integrated circuit based on the results of thecalibration mode.
 39. The method of claim 37, further including: (a)performing a first calibration mode pass through the direct IF pathbypass switch; (b) performing a second calibration mode pass through atleast one RF transceiver front-end circuit; and (c) subtracting theresults of the first calibration mode pass from the results of thesecond calibration mode pass.
 40. The method of claim 30, furtherincluding selectably connecting one or more offsetting impedances to atleast one of the primary RF transmission path or primary RF receptionpath to offset impedance mismatches due to asymmetric loading of one ormore switchable internal calibration paths during the calibration mode.41. The method of claim 30, wherein at least one phase-attenuation coreincludes a signal amplitude control circuit that includes an attenuatorcircuit for providing a reduction in amplitude of an applied signal. 42.The method of claim 30, wherein at least one phase-attenuation coreincludes a signal amplitude control circuit that includes a n amplifierthat amplifies an applied signal to effectively provide negativeattenuation.
 43. The method of claim 30, wherein at least one switchableinternal calibration path is a switchable cross-circuit calibration pathbetween at least two RF transceiver front-end circuits and the primaryRF reception path and configured for conveying, in the calibration mode,the RF test signal from the primary RF transmission path through such atleast two RF transceiver front-end circuits to the primary RF receptionpath.
 44. The method of claim 43, wherein at least one RF transceiverfront-end circuit includes an input/output circuit, and wherein at leastone switchable cross-circuit calibration path is a peripherycross-circuit calibration path configured for conveying, in thecalibration mode, the RF test signal from the primary RF transmissionpath through at least a portion of such input/output circuit of such atleast one RF transceiver front-end circuit to the primary RF receptionpath.
 45. The method of claim 30, wherein at least one switchableinternal calibration path is a switchable bypass circuit calibrationpath between at least one RF transceiver front-end circuit and theprimary RF reception path and configured for conveying, in thecalibration mode, the RF test signal from the primary RF transmissionpath through such at least one RF transceiver front-end circuit directlyto the primary RF reception path.
 46. The method of claim 45, wherein atleast one RF transceiver front-end circuit includes an input/outputcircuit, and wherein at least one switchable bypass circuit calibrationpath is a bypass periphery circuit calibration path configured forconveying, in the calibration mode, the RF test signal from the primaryRF transmission path through at least a portion of such input/outputcircuit of such at least one RF transceiver front-end circuit directlyto the primary RF reception path.
 47. The method of claim 30, furtherincluding minimizing the effects on the RF test signal of all but one ofthe coupled at least one RF transceiver front-end circuit so as torelatively isolate any remaining coupled RF transceiver front-endcircuits.
 48. The method of claim 30, further including minimizing theeffects on the RF test signal by RF transceiver front-end circuits notbeing calibrated but conveying the RF test signal, by configuring suchRF transceiver front-end circuits to a minimum amplitude adjustment. 49.The method of claim 30, further including minimizing the effects on theRF test signal by RF transceiver front-end circuits not conveying the RFtest signal, by configuring such RF transceiver front-end circuits tomaximum attenuation.
 50. The method of claim 30, further includingminimizing the effects on the RF test signal by RF transceiver front-endcircuits not conveying the RF test signal, by configuring eachswitchable internal calibration path coupled to such RF transceiverfront-end circuits to an open state.
 51. The method of claim 30, furtherincluding: (a) coupling a switchable termination circuit to the at leastone RF transceiver front-end; and (b) minimizing the effects on the RFtest signal by such RF transceiver front-end circuits not conveying theRF test signal, by configuring such switchable termination circuits to ashunt mode.
 52. The method of claim 30, further including: (a)minimizing the effects on the RF test signal by RF transceiver front-endcircuits not being calibrated but conveying the RF test signal, byconfiguring such RF transceiver front-end circuits to a minimumamplitude adjustment and approximately zero phase shift; and (b)minimizing the effects on the RF test signal by RF transceiver front-endcircuits not conveying the RF test signal, by configuring such RFtransceiver front-end circuits to maximum attenuation and by configuringeach switchable internal calibration path coupled to such RF transceiverfront-end circuits to an open state.
 53. The method of claim 30, furtherincluding conveying the RF test signal through at least two RFtransceiver front-end circuits.
 54. The method of claim 30, furtherincluding concurrently conveying the RF test signal through at least twoparallel sets of at least one serially-connected RF transceiverfront-end circuit.
 55. The method of claim 30, further includingperforming an initial calibration mode when the RF integrated circuit ismanufactured.
 56. The method of claim 30, further including adjustingdesired performance parameters of the RF integrated circuit based on theresults of the calibration mode.
 57. The method of claim 30, furtherincluding mapping nominal phase and amplitude control states to actualphase shift and amplitude levels determined during the calibration mode.58. The method of claim 30, further including varying the RF test signalover a desired frequency range.
 59. The method of claim 30, furtherincluding performing the calibration mode periodically after the RFintegrated circuit is manufactured to take into account an actual usageenvironment.
 60. The method of claim 59, wherein the actual usageenvironment includes temperature.